Isomerization of saturated hydrocarbons



Patented Dec. 17, 1946 IS ORIERIZATION 0F SATURATED HYDROCARBONS Joseph D. Danforth, Riverside, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application February 11, 1943, Serial No. 475,515

8 Claims.

This application is a continuation-in-part of my co-pending application Serial No. 370,323, led December 16, 1940.

The present invention relates to the catalytic isomerization of saturated hydrocarbons such as butane, pentane, hexane, naphthenes such as cyclohexane or hydrocarbon fractions boiling Within the gasoline range containing substantial quantities of these hydrocarbons. More specifically it deals with an improved isomerization process wherein the catalyst in the reaction zone is constantly being renewed by the introduction of fresh catalyst to said zone in solution in at least a portion of the hydrocarbon charge.

The previously proposed processes for the isomerization of saturated hydrocarbons with catalysts of the Friedel-Crafts type generally one or more halides of aluminum, zirconium, zinc, iron and the like, in the presence ofhydrogen halides consisted of passing the hydrocarbons and hydrogen halide through a fixed bed of granular catalysts either alone or deposited on solid supports under conditions of temperature and pressure such that a portion of saturated hydrocarbons are converted to isomers thereof. One of the most serious disadvantages in these processes is the decrease in catalyst activity during the course of reaction due to depletion or contamination of the active catalytic materials present. Due to the continual change in catalyst activity during the operation, it is necessary to vary the operating conditions to compensate for losses in activity in order to maintain a suitable conversion of the saturated hydrocarbons to isomers thereof. This variation in operating conditions introduces additional diiculties and complications in the operation and results in a decrease in the commercial applicability of the proposed isomerization processes. In spite of the adjustment of operating conditions, the catalyst activity decreases to an extent Where it is no longer commercially feasible to continue the operation which necessitates discontinuing the isomerization and replenishing the catalyst in the reaction zone. Various modications of operating procedure, such as the use of a plurality of reaction zones have been proposed but these modifications, multiply to a considerable extent the operating difculties encountered.

The present invention provides an improved method wherein a more continuous and substantially more economical process than has been hitherto possible is obtained.

In accordance with the present invention at least a part of the saturated hydrocarbon charge in substantially liquid phase is passed through a contact zone containing a metallic halide of the Friedel-Crafts type under conditions of temperature and pressure such that an amount of catalyst adequate to maintain the desired catalyst concentration in a subsequent reaction zone is dissolved in the liquid hydrocarbon. The catalyst containing solution from said contact zone is reacted in the presence of a hydrogen halide in a reaction zone maintained under conditions of temperature and pressure sufficient to convert a substantial portion of the saturated hydrocarbons to isomers thereof. The desired concentration is maintained in said reaction Zone by continuously supplying thereto small increments of fresh catalyst from a bulk supply in the first contact zone in solution in at least a portion of the saturated hydrocarbon charge. Y

To obtain satisfactory results in the present invention it is essential that some means be utilized to retain in the reaction zone at least a portion of the catalyst being introduced into said zone in solution in the hydrocarbon charge. Suit-A able materials for this retention of the catalyst may comprise granular particles or shaped bodies of solid materials such as rachig rings, burl saddles, crushed fire brick and other Well known packing materials.

During the initial period of the operation only a small portion of the catalyst entering the reaction zone is removed in the reaction products from said zone, the remaining portion adheres to the surfaces of the packing materials disposed within the zone. As the operation continues, the packing material will become saturated and a point will be reached Where the amount of catalyst being removed from the reaction zone either in the reaction products as free catalyst or combined with a portion 0f the hydrocarbons is substantially equivalent to the amount being introduced into said zone in solution in the hydrocarbon charge. After the establishment of this equilibrium the catalyst concentration will be maintained substantially constant throughout the remainder of the operation. This catalyst concentration will be in substantial excess of that in the incoming catalyst containing solution due primarily to the retention of a portion4 of the catalyst by the packing materials in the reaction zone.

In one specic embodiment, the present invention relates to a process for isomerizing saturated hydrocarbons which comprises passing a stream of said saturated hydrocarbon in substantially liquid phase through and in relative moveence of the catalyst supplied thereto froml the.

rst zone.

I have discovered that by introducing the catalyst into the reaction zonein solution in, at

least a portion of the hydrocarbon .charge the desired amount of catalyst may be transferredfrom the bulk supply to the reaction chamberat comparatively low temperatures. If, on the other hand, vapors of the hydrocarbon chargeare used as a carrying medium, higher temperatures4 must, be utilized-to carry an equivalent amount ofgcatalyst.` The `use of higher temperatures causes considerable,decomposition of the charging stock in the catalyst supply zone resulting ,in increased catalyst consumption due to thevformation of hydrocarboncatalyst complexes by the reaction of the catalyst with the decomposition products.

Utilization of liquid phase transfer also provides a simple method of regulating the rate of catalyst introduction. This rate will be primarilydependent upon the temperature in the supply zone which will control the solubility of the catalyst in the hydrocarboncharge. With vaporphase transfer, the rate of catalyst introduction willbe dependent not only on the temperature but also on the pressure which considerably increases complexityvof vthe operation.

Furtherfeatures and advantages of the present invention will be evident from a consideration of the follow-ingpdescription of the accompanying diagrammatic drawing of one type of apparatus in which the objects .of the invention may be, accomplished.

For simplification such units as heat exchgnrgers;` condensers, reboilers, etc., which are not essential to the lunderstanding of the description have been eliminated.A

Referringto the drawing, a saturated hydrocarbon,v forexample, normal butane, is introduced through line I containing valve 2 into pump 3 which discharges through line `l containing vvalve i 5 into heating coil I0 disposed within furnace I I The heat absorbed by the butane during its Ypassage through heating coil I0 is suiflcienttocompensate for any losses in heat during the transfer Yof the heated butane streamv through line I2 containing, valve I3 and still maintain ,the desired temperature in catalyst supply tower I4.. The temperature within tower I4 is dependent upon* the particular isomerization catalyst used andthe solubility of the catalyst in the hydrocarbon. In the broader aspects of the invention, this temperature is within the range of about .100 to about 350 F. However, narrow rangesY areapplicable to the particular isomerization catalyst utilized for example, a temperature range of approximately 140 to 250 F. is desirable when employing an aluminum chloride while with other metallic halides, such as zirconium chloride Vand zinc chloride, a higher temperature up to approximately 350 F. may be used.` The pressure in towenlftwill vary with the temperaturehut. itis essential that a liquid phase. be. maintained. within. said, tower.

3. Passed throughsaidtower perunit time.

The catalyst disposed within tower I4 may comprise aluminum chloride, zinc chloride, zirconium chloride either alone or in admixture with one another or any other well-know Friedel- Crafts type isomerizing catalyst which possesses sufficient solubility in the hydrocarbons being charged, under the particular conditionsof ternperature and pressure maintained in tower I4 to dissolve an adequate amount to maintain the desired catalyst concentration in the subsequent reactor.

For. a completely continuous operation, it is desirable to have a second tower similar to tower Mithrough which theA hydrocarbon stream may lne-converted while tower I4 is being relled with catalysts. The emuent solution in tower I4 is directed through line l5 containing valve I6 into reactor VI wherein it is commingled with a hydrogen halide obtained as hereinafter set forth. The temperatures and pressures maintained in reactor I'Iare dependent upon the hydrocarbon and. Catalyst being utilized in the operation. When utilizing aluminum. `chlorideas, the isomerizing catalyst this temperature will be ordinarily within the approximate range of to 300 F. With various other catalysts good conversions are obtained upto temperatures of about 40095F. Thefpressure is dependent upon the hydrocarbonV phase desired in reactor II. I have found that the isomerization reaction will proceed-satisfactorily in the liquid, mixed or vapor phase.

In the preferred mode of operation, reactor Il is packedv with any of `the well-known packing materials such as rachig rings, berl saddles, crushed fire-brick, etc. This packing provides a surface -uponwhich a portion of the catalyst may deposit so that vatv all times during the operation the amount of catalyst present in` reactor II is greater than that being introduced in the hydrocarbon stream from-catalyst supply tower I4.

As a specific modification of the operation, a portion of the-butane leaving pump 3 may be directedfto line 6 vcontaining lvalve I into heatingv coil v8disposed within furnace 9 wherein it is heated, -to the desired temperature and transferred through line dI-containingvalve 42 into reactor I'I.- Thisy method of operation increases to a considerable vextent the ,flexibility of the regulationorthe temperature and catalyst concentration within reactor; I l. The amount of catalyst-'removed from tower I4 is dependent primarily'upon the solubility of the catalyst in the hydrocarbon and the amount of hydrocarbon It is obvious that by varying the proportionsvof the two streamsv entering furnaces 9 and II, respectively, theamount of catalyst Vcarried into reactor I'I may be varied while maintaining a constant charge of hydrocarbons to said zone. The hydrocarbon Vstream passing through, furnace 9 may be heatedY to a temperature substantially in excess of that desired in catalyst tower I4 and can be vutilized as a heat carrying medium to produce the desired temperature when commingled with; the.,cata1yst` containing stream fromtowerll! andthe added yhydrogen halide within reactorv II.- Further advantages ,are` obtained in that this method of operating obviates the, necessity bycontactinggthebulk-supply of catalystgwith thegentire charging stock. This is extremely important inthe event, that Vthe charging stock containsgimpurities which may poison orconsume the catalyst.

Duringthereactiona minor amount of the hydrocarbon reacts with the catalyst to form a complex commonly termed sludge which is withdrawn from reactor l1 through line i8 containing valve I9; The remaining reaction products are directed through line containing valve 2l into hydrogen chloride separator 22 wherein the hydrogen chloride and light hydrocarbon gases, such as ethane and propane formed during the reaction are separated from the isobutane and unconverted normal butane. The hydrogen chloride and a portion of the light hydrocarbon gases are recycled through line 35 containing valve 40 into reactor I1. The original charge of hydrogen chloride and any additional make-up necessary during the operation is introduced through line 38 containing 4valve 39 into recycle line 35. The concentration of hydrogen chloride in reactor l1 is dependent upon the particular conversion temperature and hydrocarbon charge, but is ordinarily Within the approximate range of 1 to 40 mol per cent of the hydrocarbon and preferably within the approximate range of 5 to 25 mol per cent.

I have found that the addition of hydrogen in some instances increases the eiciency of the operation. This hydrogen may be introduced along with the hydrogen chloride through line 38 containing valve 39 into recycle line 35. The amount of hydrogen introduced will usually be less than approximately mol per cent of the hydrocarbon charge. Further addition of hydrogen may be made through line 43 containing Valve 44 into catalyst supply tower I4. To avoid a buildup of light hydrocarbons, such as methane, ethane and propane in the system, a portion is periodically withdrawn through line 36 containing valve 31 and the saturated gases'recovered as a product of the reaction after the removal of the hydrogen chloride therefrom.

The isobutane-normal butane stream is directed from separator 22 through line 23 containing valve 24 into fractionator 25 wherein the isobutane is separated from the unconverted normal butane. The separated isobutane is withdrawn through line 23 containing valve 2l and `recovered as a product of the reaction. Theunconverted normal butane is directed through line v28 containing valve 29 into pump 30 which discharges through line 3| containing valve 32 into line I2. A portion of the recycle normal butane may be directed through line 33 containing Valve 34 into reactor l1 along with the heated butane stream from furnace 9.

The following examples are presented as being characteristic of the results obtained when operating in accordance with the present invention, although it is not intended to limit the generally broad scope of the invention to the specific conditions presented in the examples.

Eample 1 into a packed reaction zone. The butane stream Acontaining aluminum chloride dissolved therein amounted to about 47 per cent of the total mixture. Hydrogen chloride was introduced into the Eample 2 Y A normal pentane fraction heated to F. was introduced into a catalyst pickup chamber containing a bed of granular aluminum chloride. The chamber was maintained under a pressure of 260 pounds per square inch. Hydrogen was introduced to the pickup chamber in an amount equivalent to 10 mol per cent of the hydrocarbon charge. The eiiluent liquid having an aluminum chloride concentration of about 1.1 pounds of aluminum chloride per barrel of charge was commingled with hydrogen chloride in a packed reaction zone maintained at a temperature of 250 F. and under a pressure of 250 pounds per square inch. The hydrogen chloride concentration in the reaction zone was 10 mol per cent of the pentane charge. A conversion' of about 45.5 per cent by volume of the charge to isopentane was obtained during the passage of the normal pentane through the packed reaction zone.

Example 3 A 39 octane number acid-treated hexane fraction was introduced into a catalyst pickup chamber containing a bed of granular aluminum chloride. The catalyst pickup chamber was maintained at a temperature of 170 F. and under a pressure of 500 pounds per square inch. The eiiluent liquid from the pickup chamber having an aluminum chloride concentration of about 1 pound per barrel of hexane charge was commingled with about 10 mol per cent of hydrogen chloride in a packed reaction tower. The octane number of the product was about 72.3, an improvement of 33.3 octane numbers over the charge.

I claim as my invention:

1. An isomerization process which comprises subjecting an isomerizable saturated hydrocarbon to catalytic isomerization in a reaction zone containing a solid packing material and maintained under isomerzing conditions, maintaining in a catalyst supply zone a bed of fresh Friedel-Crafts metal halide catalyst not previously used in said reaction zone, heating a liquid stream of said isomerizable saturated hydrocarbon to a temperature sufficient to dissolve a portion of said catalyst, thereafter passing the heated stream in substantially liquid phase through said bed in the supply zone and dissolving a portion of the bed in the liquid stream, introducing the resultant catalyst-hydrocarbon solution to the reaction zone and depositing catalyst from the solution onto said solid packing material to maintain in the reaction zone a catalyst concentration substantially greater than that of the solution be.- ing introduced to the reaction zone, effecting said catalytic isomerization of the saturated hydrocarbon in the presence of the catalyst thus retained in the reaction zone, substantially all of the requisite quantity of fresh metal halide catalyst for effecting said catalytic isomerization being supplied to the reaction zone in said solution, removing resultant reaction products from the reaction zone and supplying the same to a fractionating zone without passage thereof through the catalyst supply zone, and fractionating the products in the fractionating zone to recover the isomerized hydrocarbon therefrom.

2. A process for isomerizing an isomerizabl'e saturated hydrocarbon-which comprises heating a liquid stream comprising aiportionof saidhydrocarbon and then passing the 4heated stream in substantially liquid phase :through a bed of fresh Friedel-Crafts metal v'halide catalyst at a temperature sulicientto dissolve a portion of said bed, introducing the resultant catalyst-hydrocarbon solution to a reactionzone containing a solid packing material, separately heatinga second portion of said hydrocarbon to ya higher temperature than the nist-mentioned portion and then introducing the same directly-to Ythe reaction zone, the amount and temperature 'ofi said separately heated' second portion being suilc'ient to maintain an isomerizing temperature in the reaction zone, depositing catalyst f'rom said solution onto said solid packing material to maintain in the reaction zone a catalystconcentration substantially greater 'than that-of said 'solution, effecting substantial isomerization of said portions of the hydrocarbon in `the presence of the catalyst thus retained in 'the reaction zone. substantially all of the requisite-quantity of fresh metal halide catalyst for eiiecting said catalytic isomerization being supplied tothe reaction zone in said solution, removing resultant reaction products from said zoneand recovering the isomerized hydrocarbon therefrom.

3. An isomerization process which comprises subjecting an isomerizable saturatedhydrocarbon to catalytic isomerization in the presence of a hydrogen halide in a reaction zone containing a solid packing material and maintained under isomerizing conditions, maintaining in a catalyst supply zone a bed of fresh aluminum halide catalyst not previously used in said reaction zone, heating a liquid stream ofV said isomerirable` saturated hydrocarbon to a Atemperature sufficient to dissolve a portion of-said aluminum halide, thereafter passing the heated stream in substantially liquid phase through said bed in the supply zone and dissolving a portion of the bed in the liquid stream, introducing the resultant aluminum halide-hydrocarbon solution to rthe reaction zone and depositing aluminum halide catalyst from the solution onto said solid packing material to maintain in the'reaction zone an aluminum halide concentration substantially greater than that of the solution being introduced to the reaction zone, effecting said catalytic isomerization of the saturated hydrocarbon in the presence of the aluminum halide catalyst thus retained in the reaction zone, substantially all of the requisite quantity of fresh alurm'num halide catalyst for effecting said catalytic isomeriaation being supplied to the reaction zone in said solution, removing resultant reaction pro-ducts from the reaction zone and supplying the same to a fractionating zone without passage thereof through the catalyst supply zone, and fractionating the products in the fractionating zone to recover the isomerized hydrocarbon therefrom.

4. An isomerization process which comprises subjecting an isomerizable saturated hydrocarbon to catalytic isomerization in the presence of hydrogen chloride in a reaction zone containing a solid packing material and maintained under isomerizing conditie-ns, maintaining in a catalyst supply zone a bed offresh aluminum chloride catalyst not previously used in said reaction zone, heating a liquid stream of said isomerizable saturated hydrocarbon to a temperature'sufficient to dissolve aluminum chloride therein, thereafter passing the heated stream in substantially liquid phase through said bed in the supply zone and .dissolving a-'portion of the bed in the liquid stream',fintroducing the resultantaluminum chloride-hydrocarbon ksolution tothe' reaction zone 'and depositing aluminum chloride-catalyst from the solution onto said solid packing `material rto maintain in the reaction zonean aluminum chloride concentration substantially greater lthan that of the solution being introduced 4to the re- .action zone, effecting said catalytic isomerization of' the saturated hydrocarbon in the lpresence of the aluminum chloride catalyst Ithus retained in the reaction zone, substantially all of the requisitequantity of fresh aluminum chloride catalyst for eiecting said catalytic isomerization being supplied to the'reac'tion zone in said solution, removing resultant reaction products fromxthe reaction zone and supplying the same to a fractionating zone Without passage thereof through the catalyst supply zone, and fractionating the products in lthe fractionatingezone to recover the isomerized hydrocarbon therefrom.

5. A process for isomerizing an isomeriz'able saturated hydrocarbon which comprises .heating a liquid stream comprising a portion of said hydrocarbon and then 'passing the heatedv stream in substantially liquid phase .through .a `bed of fresh .aluminum halide at altemperature. sufficient to dissolve afportion of said bed, 'introducing the resultant aluminum halide-'hydrocarbon solution and a hydrogen .halide toza reaction zone containing a solid packing material, separately heating a second portion of said hydrocarbon to a higher temperature than thev first-mentioned portion and then introducing the same `.directly to the reaction zone, the amount and .tempera-- ture of said separately heated second portion being suicient to maintain an visomerizing temperature in the reaction zona-.depositing .aluminum halide catalyst from 4said Asolution onto said solid packing material to'maintain in the reaction zone an aluminum halideconcentration substantially greaterthan thatof said solution, effecting substantial isomerization of said portions of the hydrocarbon inthe presence -of the aluminum halide-catalyst thus' retained in the reaction zone, substantially all. of v therequisite quantity of fresh-aluminum halide catalyst for effecting said catalytic isomerizationbeing supplied to the reactionA zone in said solution, removingfresult'ant reaction products from Isaid zone and recovering the isomerized hydrocarbon therefrom.

6. A-process for isomerizing an -isom'erizable saturated hydrocarbon which comprises heating 'a liquid stream comprising a'portion of said'hydrocarbon to a temperature sufficient to dissolve aluminum chloride therein and then passing the heated stream in substantially liquid phase through a bed of fresh aluminum chloride to dissolve a portion of said' bed, introducing the resultant aluminum chloride-hydrocarbon solution and hydrogen chloride to a reaction zone containing a solid packing material, separately heatingaJ second portion of said hydrocarbonv to .a higher temperature than the rst-mentioned portionV and then introducing the same directly tothe reaction zone, the amount and temperature of, said separately heated second portion belng suicient to maintain an. isomerizing temperature in the reaction zone, depositing .aluminum. chloride oatalystffrom said solution onto said solid packing material tomaintain in the reaction zone an aluminumchloride concentration substantially greater thanv that :of said. solution, effecting substantial isomerization'of said portions of the hydrocarbon n the presence of the aluminum chloride catalyst thus retained in the reaction zone, substantially all of the requisite quantity of fresh aluminum chloride catalyst for effecting said catalytic isomerzation being supplied to the reaction zone in said solution, removing resultant reaction products from said zone and recovering the isomerized hydrocarbon therefrom.

10 7. The process as defined in claim 3 further' characterized in that said saturated hydrocarbon is a normal paraffin.

8. The process as defined in claim 3 further characterized in that said saturated hydrocarbon is normal butane.

JOSEPH D. DANFORTH. 

